1. Field of the Invention
The present invention relates to an electronic device having a push button structure with an illuminating function and, more particularly, to a prevention of an illuminating light leakage and a reduction in the looseness of a button operation.
2. Background
In the prior art, there is known an electronic device, which is provided with a push button having an illuminating function, as shown in FIG. 2. In the electronic device 100 of FIG. 2, an operation panel 102 is a button holding base member. The operation panel 102 is provided with a cylindrical button housing portion 104. Into this button housing portion 104, there is inserted a button 106, which is made of a resin material for transmitting an illuminating light.
On the rear side of the operation panel 102, on the other hand, there is arranged a printed-circuit board 108. On this printed-circuit board 108, there are mounted a switch 110 and a LED light source 112. The switch 110 and the LED light source 112 are disposed at positions corresponding to the button 106.
As shown in FIG. 2, the inner circumference of the button housing portion 104 and the outer circumference of the button 106 constitute a sliding portion 114. An illuminating light leakage preventing portion 116 is disposed on the front side of the sliding portion 114. Here, the front side is the side close to the surface of the operation panel 102.
In the illuminating light leakage preventing portion 116, the button housing portion 104 is provided with a step 118. As a result, the button housing portion 104 is expanded on the front side. The button 106 is also provided with a step 120 corresponding to the step 118 of the button housing portion 104. As a result, the button 106 has an expanded head portion. This step structure prevents the illuminating light leakage. Moreover, a clearance corresponding to the button stroke is established between the step 120 of the button 106 and the step 118 of the button housing portion 104.
In the electronic device 100 of FIG. 2, the LED light source 112 is turned ON so that the light passes through the button 106 so that the button 106 glows. The leakage of the light is prevented by the illuminating light leakage preventing portion 116. When the button 106 is pushed, the button housing portion 104 and the button 106 slide in the sliding portion 114.
In the conventional structure of FIG. 2, as described above, both the button sliding structure and the illuminating light leakage preventing structure are juxtaposed to each other in the button housing portion 104.
Another illuminating light leakage preventing structure of the button with the illuminating function is disclosed, for example, in JP-A-2000-340071 (pages 3 and 4, FIG. 1) and JP-A-2001-307595 (pages 4 and 5, FIG. 1). In these Publications, the illuminating light leakage of a seesaw button is prevented by using the flange on the button outer circumference.
In the conventional electronic device of FIG. 2, the sliding structure and the illuminating light leakage preventing structure are juxtaposed in the button housing portion. Therefore, the illuminating light leakage preventing structure has to be retained by sacrificing the space for the sliding structure. In FIG. 2, the illuminating light leakage preventing structure needs the space for the button stroke so that the sliding distance is shortened. This short sliding distance lowers the ability of preventing the looseness of the button.